As human beings continue migrating to cities, and as commercial transport and the transport of human beings themselves are increasingly carried out on a finite number of roads, problems such as traffic congestion, pollution, and accidents become worse. Meanwhile, conventional forms of air transportation, such as airplanes, not only require runways and hangars, but also result in nearly 100% mortality when there is a crash. Consequently, air transportation is generally less accessible and regarded with more fear when compared to ground transportation.